DEPOSITION OF DIAMOND-LIKE CARBON USING A PLANAR RADIO-FREQUENCY INDUCTION PLASMA

The use of a planar radio frequency inductively coupled plasma for the preparation of diamondlike carbon (DLC) thin films is investigated. This approach offers a number of advantages over conventional rf parallel plate plasma processes for studying the deposition of DLC. In the latter case, substrate ion bombardment energy is determined by the rf self-bias which is a function of discharge power. For the rf induction plasma, discharge power absorption and rf substrate bias are decoupled, allowing independent evaluation of the effects of each parameter. Along with these quantities, the influence of CH4 flow rate and Ar dilution are investigated. Film properties examined include hardness, stress, optical transmittance, and hydrogen concentration. In addition, plasma optical emission spectra have been collected under various conditions. Films deposited at room temperature are found to be typical of DLC prepared by conventional plasma enhanced chemical vapor deposition processes, with microhardness values up to 30 GPa, optical bandgaps between 1.3 and 1.8 eV, and hydrogen content ranging from 20% to 36%. The planar geometry and high degree of dissociation in the rf induction plasma permit the coating of large areas at high rates (>1000 angstrom/min). Other observations include a maximum in the hardness versus substrate bias curve.